In this section, we will discuss the connection of our results to
those from the TMD factorization formalism. Here we just give a concise
comparison between the results from our approach and those from the
TMD factorization formalism. The details of the TMD factorization
formalism applied to UPC can be found in Refs. [1]}, [2]}, [3]}, [4]}.
The recent developments in the impact-parameter dependent cross sections
in terms of photon Wigner functions are given in Ref. [5]}, [6]}.
